Shock and static pressure discriminating switch



Oct. 25, 1955 R. c. KENT, JR 2,721,913

SHOCK AND STATIC PRESSURE DISCRIMINATING SWITCH\ Filed July 17, 1950 43 grwmm RAYMOND C. KENT, JR.

Wan a SHOCK AND STATIC PRESSURE, DISCRIMINATING swrrcu This invention relates generally to circuitmakers and more particularly to anew and; improved pressure responsive switch adapted to close an electric circuit in respouse to a predetermined hydrostatic pressure while also having the unique characteristics of remaining substantially unaffected by suddenly applied shock pressures which, if applied statically, would operate the switch to circuit closed position.

Hydrostatic switches of this general type have been extensively employed in various forms of underwater ordnance such, for example, as mines, torpedoes, depth charges and the'like wherein these switches operate to electricallyarm or render safe, as the case may be, such weapons as they reach a predetermined depth of submergence. In,torpedoes,'suc hswitches have, of late, been so arranged with respect to' the firing control system thereof that as thetorpedo is launched from'a submarine. operating at a considerable depth below the sur- 1 face of the water the surrounding pressure .is eifective to actuate these switches to close an electric shorting circuit across the firing circuit of. the torpedo whereby premature firing thereof is prevented'as the torpedo rises to striking position with the-target vessel.

. .Although this, arrangement in torpedoes of switches of this type for the purpose/indicated has been found generally satisfactory there is always the possibility that anti-torpedo explosivedevices, frequently found arranged about the target vessel. and adapted to be detonated by acoustic signals received from the approaching torpedo will, when sodetonated, produce within the surrounding water apressure shock wave of such amplitude as to actuate these switches to circuit closed position thereby to again connect across the firing circuit ofthe'torpedo the shorting circuitto render the torpedo inoperative at a time when the torpedo would otherwise be detonated by contact with the target vessel.

In an eifort to forego the possibility of such a con- .dition occurring, various forms of switches and mechanical lockin arrangements therefor have been devised,

tested and ultimately discarded in favor of the switch of the present invention which possesses the characteristics of responding readily to slowly applied pressures as may result from the launching of a torpedo from an.

undersea craft while remaining substantially unaifected by shock pressure as may be applied thereto from the detonation from close proximity therewith of counter mine apparatus. V i

It has been found that by providing'a switch wherein the pressure respo'nsive element thereof is composed of a suitable plastic material and so formed that the diameter thereof is substantially equal to or less than its thickness and secured fixedly, as by bonding, to the. side wall sections of the switch housing rather than by crimping thereto'in the conventionalmanner of such diaphragm securement, as is generally practiced in switches of this type heretofore devised, the material of the element is caused under pressure to flow gradually toward switch closing position at a rate controlledby the plastic flow Ratented Oct. 25, 1955 characteristics of the material of which the element is composed regardless of the rate at whichthe pressure is applied whereby a switch possessing wide ranges of pressure response and shock pressure resistance is provided.

.It is an object of the present invention to provide a new and improved pressure responsive switch adapted to selectively distinguish between static and shockpressures of varying amplitudes and durations.

A further object is to provide a pressure responsive switch wherein the pressure response thereof is controllable by the plastic flow characteristics of the pressure responsive element thereof. l I

A further object is to provide anew and improved pressure responsive switch wherein the pressure sensitive element thereof is cast integrally with the switch housing.

It is a still further object tov provide a pressure responsive switch wherein the pressure responsive elementthereof is formed of resilient material having high plastic flow resistance characteristicsand of a thickness substantially equal to orgreater than the diameter thereof. I v

Other objects and many of the attendant advantages of this invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein: I

Fig. l is a sectional view through the switch of the instant invention according to the preferred embodiment thereof and showing the switch in its initial or open circuit position; I Fig. 2 is a sectional view of the switch of Fig. 1 as shown in operated or circuit closed position;

Fig. 3 is a cross sectional view taken along the line 33 of Fig. 2; and

Fig. 4 is a sectional view of an alternate arrangement of the switch of the present invention illustrated in the open circuit position. i

Referring now to the drawings for a more complete understanding of the invention and more particularlyto Figs. 1, 2 and 3 thereof, theswit ch according to the preferred embodiment of the present invention is generally designated 5 and includes the cylindrical housing member 6 wherein an annular groove 7 is formed about the outer surface thereof for retaining therein a conventional 0 ring gasket 8 adapted to provide a high pressure seal between the switch and exploder mechanism,1not

shown, and by means of which the switch is generally mounted for assembly within the casing of a torpedo.

Preferably cast integrally with the switchhousing .is a pressure responsive element 9 of any suitable resilient plastic material havinghighplastic fiow resistance-characteristic suchQfor example, as silicon rubber or the like, the requirements for this element being to slowly respond to and recover from pressures applied thereto from the direction of the surface 10 thereof. The formation of this element 9 is such that the thickness thereof is substantially equal to or greater than its diameter, as h asbeen-he'reinbefore indicated. v

Arranged; as illustrated, over the element 9 is'a protective cover plate 11 formed of thin corrugated beryllium copper or plastic impregnated fabric orv the like and secured to the switch housing as by the crimped flange portion 12 of the'latter. The material of the cover plate 11 by being thusly formed and so arranged offers relatively little resistance to pressure applied therethrough to the surface 14) of the element 9 and yet the cover serves to prevent possible damage being done to the element that could otherwise effect its pressure responsive characteristics.

Secured as by bonding to the inner surface 2"of the element 9 and movable inwardly by deformation of the latter is an annular member 13 having projecting" downwardly therefrom a rounded end contact portion 14 formed from suitable conductive material such, for example, as brass, copper or the like and preferably silver plated to provide a low resistance contact surface for a purpose which will become more clearly apparent as the description proceeds.

The arrangement of the member 13 with respect to the element 9 is such that, as the element is depressed inwardly responsive to pressure of the desired character being applied to the surface 10 thereof, the contact portion 14 of the member 13 is urged thereby downwardly within a guide bore 15 provided therefor in an insulating plug member 16 and which is secured for vertical adjustment within the switch housing by threadedly connecting with a sleeve member 17 secured, as illustrated, Within a recessed portion 18 of the housing as by a crimped flange portion 19 of the latter.

The insulating plug 16 has provided in the lower portion thereof a transversely arranged slot 21 for receiving a screw driver or like tool for rotation of this plug for vertical adjustment within the threaded section 22 of the sleeve 17.

The plug 16 is provided across its upper end portion with a transverse slot 23 within which is accommodated, at the time of assembly, the angular portions of a pair of terminal pins 25 as the elongated vertical portions of the pins are received for press fitting within arallel bores provided therefor in the lower or solid end section of the plug 16, as illustrated. The angular portions of the pins are provided with chamfered end portions 26 and arranged in close but spaced adjacency whereby a bridging contact may be established therebetween as the contact member 14 is urged thereagainst by suflicient inward movement of the element 9. The vertical adjustment of the plug 16 within the threaded section 22 of the sleeve 17, as heretofore set forth, provides for increasing or reducing the gap between the contact portion 14 of the member 13 and the chamfered portions 26 of the pins 25 whereby the degree of deformation of the element 9 required for closing the switch may be selectively varied.

Fig. 2 illustrates the switch of Fig. 1 in operated position with the cover plate 11 and element 9 thereof deformed inwardly to the extent of bringing the contact member 14 into spanning connection with the contact portions 26 of the pins 25 whereby the circuit is thusly completed through the switch.

An alternative arrangement of a switch embodying the features of the present invention is shown in Fig. 4 to include a cylindrical switch housing 30 formed substantially in the same manner as that of Fig. 1 and including an ring gasket 31 arranged as illustrated about the outer surface of the switch housing and whereby a pressure seal is maintained about the switch when mounted within the casing of a torpedo, not shown. Instead of the element 9 being cast integrally with the switch housing 30 as in the case of the switch of Fig. 1, the element 9 is secured as by bonding within a cylindrical insert 32 telescopically arranged within a closely fitting bore 33 provided therefor in the upper end portion of the switch housing and wherein the sleeve is secured by a flange portion 34 of the housing which is crimped thereover in the manner illustrated. A ring gasket 35 compressed by the flange 34 to the end of the sleeve 32 provides a pressure sealing connection therebetween whereby fluid to which the outer surface of the switch is exposed is prevented in this manner from entering the switch housing 30 between the sleeve 32 and the surface of the bore 33.

Secured integrally with the element 9, as by bonding thereto at 50, is an annular member 36 having a contact portion 40 movable, responsive to inward deformation of the element 9, downwardly through an annular opening 37 provided as a guide therefor in an internal flange section 38 of the switch housing 30. An annular Bellsville spring washer 39 interposed between the member 36 and the flange 38 provides an electrical connection therebetween and whereby the housing 30 is in this manner made one terminal of the switch. The spring washer 39 may be formed from beryllium copper or like material having suitable resilient and electro-conduc tive characteristics.

Adjustably secured as by the threads 41 within the lower end of the switch housing 30 is an internally flanged sleeve 42 wherein is cast, integrally therewith and about a centrally grooved contact member 43, a mass of insulating material 44 such, for example, as plastic or hard rubber or the like and adapted to electrically insulate the contact member 43 from the sleeve and switch housing 42 and 30 respectively. Bores 45 formed in the lower end of the flange portion 46 of the sleeve 42, as indicated, permit the connection therewith of a spanner wrench or like tool whereby the sleeve may be rotated within the housing for decreasing or increasing the distance between the contact portion 40 of member 36 and the contact member 43 whereby the pressure response of the switch may in this manner be selectively regulated.

Referring now briefly to the operation of the device and more particularly to that shown in Fig. 1, the switch 5 when secured within an extender mechanism, not shown, and mounted conventionally within the side wall sections of a torpedo, likewise not shown, is so arranged that the outer surface of the element 9 of the switch is exposed at all times to the pressure of the surrounding water. As the torepdo is launched from a submarine submerged beneath the surface of a body of water, the relatively static pressure of the surrounding water operates to cause a flowing of the plastic material of the element 9 of the switch toward the switch closed position of Fig. 2 and, in which case, after a predetermined time as determined by the material from which the element is composed, the contact member 14 to which the element is secured is extended downwardly into spanning engagement with the contact portions of the terminal pins 25 whereby a circuit is completed through the switch pins to the heretofore mentioned, but not shown, shorting circuit of the torpedo fire control system for rendering the torpedo safe with respect to the launching craft as it rises to striking position with the target vessel. The structure of the switch is such that by proper selection of the material of the element 9, the switch may be accurately adjusted by rotation of the plug 16 to close under relatively static pressure conditions within a satisfactorily time of approximately 500 milliseconds and at substantially any desired pressure while possessing the characteristics of remaining substantially unaffected by considerably greater shock pressures of less duration as, for example, 5 milliseconds, and such as may be produced within the surrounding water by the explosion of counter-mine or antitorpedo apparatus. Thus, in response to counter-mine shock, for example, the contact member 14 does not move to bridge the contact surfaces 26. It will be understood that the switch of Fig. 4 operates generally in the same manner as the switch of Figs. 1 to 3.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the present claims the invention may be practiced otherwise than as specifically described.

The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without payment of any royalty thereon or therefor.

What is claimed as new and desired to be secured by Letters Patent of the United States is:

1. A switch of the character disclosed for discriminating between shock and static pressure and including, in combination, an elongated housing having an opening therethrough, a deformable plastic element of high plastic flow resistance characteristic and of a thickness not less than the width thereof and arranged for closing one end of said opening, an insulating plug adjustably secured to said housing for closing the other end of said opening, normally open switching means including at least one switching element carried by said plug, and means on said plastic element for closing said switching means in response to a predetermined deformation of said plastic element.

2. A switch of the character disclosed for discriminating between static and shock pressure and including, in combination, a housing having therein an elongated bore, a cylindrical plastic element of a thickness substantially equal to or greater than its diameter arranged for closing one end of said bore, an insulating plug adjustably secured to said housing for closing the other end of said bore, a contact member carried by said plug and electrically insulated thereby from the housing, and a contact element carried by said plastic element and electrically connected to said housing and movable by pressure responsive deformation of said plastic element into circuit closing engagement with said contact member.

3. A static and shock pressure discriminating switch of the character disclosed including, in combination, a housing adapted for connecting within the casing of a torpedo and including an opening therethrough, a plastic element of high plastic flow resistance characteristics and of a thickness substantially equal to or greater than its width bonded to the housing within said opening for closing one end thereof, a contact element carried by said plastic element and movable thereby responsive to plastic deformation of the latter, a second contact element electrically insulated from said housing, and means for adjusting said second contact element for contact engagement by the first said contact element as said plastic element is deformed in response to a predetermined pressure applied thereto.

4. A static and shock pressure discriminating switch of the character disclosed including, in combination, a cylindrical housing having a centrally arranged opening therein, a cylindrical plastic element of high plastic flow resistance characteristic and of a length substantially equal to or greater than the diameter of said opening and bonded therein along its length for closing one end of said opening, a contact member carried by said element and movable longitudinally inwardly within said opening upon inward deformation of said element, an insulating plug secured for adjustable movement within the other end of said opening, and a pair of electrically spaced contact pieces carried by said plug and arranged for being connected in electrical contact by said contact member as the contact member is moved inwardly upon said inward deformation of the said plastic element in response to a predetermined pressure applied to the outer surface thereof.

5. A static and shock pressure discriminating switch of the character disclosed including, in combination, a cylindrical housing having a centrally arranged opening therein, a cylindrical plastic element of high plastic flow resistance characteristic arranged within said opening and bonded to said housing throughout its lengthin a manner to close one end of said opening, a first contact member carried by said element and movable longitudinally by inward deformation of the element responsive to a predetermined hydrostatic pressure applied thereto, means electrically connecting said contact member with said housing, an insulating plug secured for adjustment within the other end of said opening, and a second contact member carried by said plug and electrically insulated thereby from said housing and arranged for contact engagement by said first contact member thereby to close said switch upon a predetermined inward deformation of said plastic element.

6. A static and shock pressure discriminating device of the character disclosed comprising, in combination, a plastic element having a predetermined plastic flow rate such that the element is caused to flow with resultant deformation in response to pressures which are static or change at a rate equal to or less than said flow rate of the element and the element is unaffected by pressures caused by shock or pressures which change at a rate which exceeds said flow rate of the element, means for supporting said element so as to subject one face thereof to said static and shock pressures, contact means carried by said supporting means and arranged in predetermined spaced relation with respect to the opposite face of said element, and movable means including a resilient member carried by said plastic element for establishing an electrical circuit through the device as said movable means is moved into engagement with said contact means in response to a predetermined deformation of the element.

7. A switch of the character disclosed for discriminating between shock and static pressure and including, in combination, an elongated housing having an opening therethrough, a plastic element of high plastic flow resistance characteristic and of a thickness substantially equal to or greater than its diameter and arranged within said opening and bonded to said housing throughout its length for closing one end of the opening, an insulating plug adjustably secured to said housing for closing the other end of said opening, normally open contact means carried by said plug and element and actuated to a closed position in response to deformation of'said plastic element and a resilient member carried by said plastic element in engagement therewith and with said housing for establishing an electric circuit through said switch as said contact means moves to said closed position.

References Cited in the file of this patent UNITED STATES PATENTS 1,906,446 Clement May 2, 1933 2,260,636 Nefi Oct. 28, 1941 2,318,300 Durbin May 14, 1943 2,338,750 Winton Jan. 11, 1944 

